In hierarchical computer storage systems, intensively used and fast storage are paired with arrays of slower and less frequently accessed data devices. One example of high-speed, expensive memory is a direct access storage device file buffer (DASD). Slower storage devices include tape drives and disk drive arrays, which are less expensive than a DASD.
One such hierarchical storage system is a virtual tape storage system. Such a virtual tape storage system may include, for example, one or more virtual tape servers (“VTS”) in combination with one or more data storage and retrieval systems, such as the IBM TotalStorage® 3494 Enterprise Tape Library. During operation, the virtual tape storage system is writing data from a host to the numerous data storage devices disposed in the one or more data storage and retrieval systems.
More recently introduced data disaster recovery solutions include “remote dual copy,” where data is backed-up not only remotely, but also continuously (either synchronously or asynchronously). In order to communicate duplexed data from one host processor to another host processor, or from one storage controller to another storage controller, or some combination thereof, a substantial amount of control data is required for realizing the process. A high overhead, however, can interfere with a secondary site's ability to keep up with a primary site's processing, thus threatening the ability of the secondary site to be able to recover the primary in the event a disaster occurs.
Disaster recovery protection for the typical data processing system requires that primary data stored on primary DASDs be backed-up at a secondary or remote location. The physical distance separating the primary and secondary locations can be set depending upon the level of risk acceptable to the user, and can vary from several kilometers to thousands of kilometers.
The secondary site must not only be sufficiently remote from the primary site, but must also be able to backup primary data in real time. The secondary site needs to backup primary data in real time as the primary data is updated, with some minimal delay.
What is needed is an apparatus and method to autonomically optimize the rate of transmission of information between geographically separated virtual tape servers.